The transmembrane disposition of rhodopsin in the retinal rod outer segment disk membrane will be studied by proteolytic and vectorial covalent chemical labeling with new imidoester derivatives. We will attempt to isolate the transmembrane peptide proteolytic fragments of rhodopsin, determine their composition and study their conformation in recombinant membranes using circular dichroism and nuclear magnetic resonance. We will study lipid-lipid and lipid-protein interactions using carbon 13 and deuterium NMR in native ROS and recombinant rhodopsin bearing membranes. We intend to use low angle X-ray diffraction and neutron diffraction to study rhodopsin in recombinant membranes. We intend to study the effects of lipid composition on the Metarhodopsin I to Metarhodopsin II reaction. We also intend to study ion sequestration and affinities on a physiological time scale using colorimetric indicators and membrane preparations with intact, unoxidized lipids and sulfhydryls.